The EU’s submission comes after Switzerland released its commitment to a proposed global climate pact, aiming for 50% carbon cuts on 1990 levels by 2030.

All major economies are expected to deliver their INDCs to the UN by October 1 so it can assess if they will be enough to prevent warming of above 2C, a level deemed dangerous and one governments have agreed to avoid.

Jonathan Grant from accountants PwC said the 40% goal looked “ambitious” given an expected 54% rise in the EU’s economic growth from 2000 to 2030.

“The EU will need to nearly double its current rate of decarbonisation to achieve the 40% reduction target by 2030,” he said.

“By 2022 European countries will need to have the same carbon intensity as France today, which is the lowest of the G20 countries, and then cut this by a quarter by 2030.”

Jennifer Morgan, who runs the World Resources Institute climate programme, said the EU’s “early delivery” would build momentum ahead of Paris.

“Their climate package is an ambitious start, but it leaves room to go even further in the months ahead,” she said.

“We expect the EU and other countries to look for ways to strengthen their actions in the lead up to a strong, universal climate agreement in Paris.”

But while the speed of the EU’s announcement was broadly welcomed, some observers expressed disappointment the pledge did not offer more assurances on climate finance to developing countries, or offer support for a climate compensation mechanism.

“How can we adapt to climate change impacts without a commitment on finance? How can African governments scale up their climate action if they don’t know what finance and technology is available to them,” said Azeb Girmai from LDC-Watch in Addis Abba.

“The science is very clear that such weak targets, combined with the ongoing use of discredited carbon markets, means we are not on track to tackle the climate crisis, and that the EU is now complicit in committing us to further destruction,” she said.

Analysts at the Carbon Pulse website said European plans to meet its goals through its struggling emissions trading scheme would likely be further undermined after the release of free pollution permits worth “hundreds of millions of euros” to major businesses.

Fort Collin’s committment is excellent –but realistically, without a national commitment from the US, it’s less than a drop in the bucket. And even a national US commitment is small (US is only 17% of global GHG emissions), and negligible without the world going along, especially China. (~30% of emissions)